Fire resistant sound absorber

ABSTRACT

The object of the present invention is to provide a sound absorber such as a hood silencer, attached to the underside of the hood panel of a car to absorb sound from the engine, said sound absorber having excellent fire resistance and sound absorbability.  
     To attain said object, the present invention provides a fire resistant sound absorber  1  made of a porous material  2  into which a phenolic resin is impregnated, said porous material  2  using fibers with a fineness in the range of between 0.02 dtex and 50 dtex, with phenolic resin content in said porous material  2  being adjusted to be in the range of between 50 and 200% by mass per unit weight of said porous material  2.

FIELD OF THE INVENTION

The present invention relates to a sound absorber for such as the soundsfrom a car engine, said sound absorber being fire resistant.

BACKGROUND OF THE INVENTION

A hood silencer (1P) is attached to the underside of the hood panel of acar. Hitherto, a laminate of polyester nonwoven fabric (12P) such as PETon a glass wool (2P) having good heat resistance and sound absorbabilityhas been provided as a hood silencer (1P) as shown in FIG. 4(JP64-36433).

As described above, glass wool (2P) has been used as the material forthe hood silencer (1P), but there is a problem in that said glass woolis apt to sting workers' hands, resulting in a deterioration ofworkability, and further, is apt to spread minute glass fiber dust,contaminating work environment.

Furtheremore, it is necessary to laminate a nonwoven fabric (12P) ontosaid glass wool (2P) so as not to expose said glass wool in theconventional hood silencer. Still further, in the case of a hoodsilencer made of glass wool, said glass wool can not be incinerated,making said hood silencer difficult to discard.

DISCLOSURE OF THE INVENTION

To solve the above described problems, the present invention provide afire resistant sound absorber made of a porous material into which aphenolic resin is impregnated, wherein said phenolic resin isimpregnated in an amount in the range of between 50 and 200% by mass per1 m² of said porous material, and said porous material consists offibers having a fineness in the range of between 0.02 dtex and 50 dtex.

In said fire resistant sound absorber, said phenolic resin is preferablya cocondensation polymer of phenol alkylresorcin, and said alkylresorcincocondensation polymer is preferably produced by adding alkylresorcin tophenol resin precondensation polymer to cocondensate.

Fibers having a fineness in the range of between 0.02 dtex and 50 dtexare used in said porous material and 50 to 200% by mass of fireresistant phenolic resin is contained in 1 m² of said porous material.By adjusting the fineness of the fibers of said porous material and itsphenolic resin content, the fire resistance and sound absorbability arealso adjusted.

The fire resistant sound absorber of the present invention has excellentrigidity, fire resistance and sound absorbability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fire resistant sound absorber (hoodsilencer).

FIG. 2 is a perspective view of a fire resistant sound absorber (hoodsilencer) attached to the underside of the hood panel.

FIG. 3 is an explanatory diagram of the process of impregnating phenolicresin precondensation polymer.

FIG. 4 is a partial sectional view of the conventional sound absorber(hood silencer).

IN THE DRAWINGS

1. Fire resistant sound absorber (hood silencer)

2. Porous material

3. Hood panel

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is detailed as described below.

[Phenolic Resin]

Phenolic resin is produced by the condensation reaction between phenoliccompound and an aldehyde and/or aldehyde donor. Said phenolic resin maybe sulfoalkylated and/or sulfialkylated to improve its solubility inwater.

Said phenolic resin is impregnated into a porous material (2) in theform of precondensation polymer. Commonly said precondensation polymeris prepared as a water solution, but if desired water-soluble organicsolvent also can be used in the present invention. Said water-solubleorganic solvent may be alcohols such as methanol, ethanol, isopropanol,n-propanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-amylalcohol, isoamyl alcohol, n-hexanol, methylamyl alcohol, 2-ethylbutanol, n-heptanol, n-octanol, trimethylnonylalcohol, cyclohexanol,benzyl alcohol, furfuryl alcohol, tetrahydro furfuryl alcohol, abiethylalcohol, diacetone alcohol, and the like; ketones such as acetone,methyl acetone, methyl ethyl ketone, methyl-n-propyl ketone,methyl-n-butyl ketone, methyl isobutyl ketone, diethyl ketone,di-n-propyl ketone, diisobutyl ketone, acetonyl acetone, methyl oxido,cyclohexanone, methyl cyclohexanone, acetophenon, camphor, and the like;glycols such as ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, trimethylene glycol, polyethylene glycol, and thelike; glycol ethers such as ethylene glycol mono-methyl ether, ethyleneglycol mono-ethyl ether, ethylene glycol isopropyl ether, diethyleneglycol mono-methyl ether, triethylene glycol mono-methyl ether, and thelike; esters of the above mentioned glycols such as ethylene glycoldiacetate, diethylene glycol mono-ethyl ether acetate, and thelike, andtheir derivatives; ether such as 1,4-dioxane, and the like; diethylcellosolve, diethyl carbitol, ethyl lactate, isopropyl lactate, diglycoldiacetate, dimethyl formamide, and the like.

(Phenolic Compound)

The phenolic compound used to produce said phenolic resin may bemonohydric phenol, or polyhydric phenol or a mixture of monohydricphenol and polyhydric phenol, but in a case where only monohydric phenolis used, formaldehyde is apt to be emitted when or after said resincomposition is cured so that polyphenol or a mixture of monophenol andpolyphenol is desirably used.

(Monohydric Phenol)

The monohydric phenols include alkyl phenols such as o-cresol, m-cresol,p-cresol, ethylphenol, isopropylphenol, xylenol, 3,5-xylenol,butylphenol, t-butylphenol, nonylphenol and the like; monohydricderivatives such as o-fluorophenol, m-fluorophenol, p-fluorophenol,o-chlorophenol, m-chlorophenol, p-chlorophenol, o-bromophenol,m-bromophenol, p-bromophenol, o-iodophenol, m-iodophenol, p-iodophenol,o-aminophenol, m-aminophenol, p-aminophenol, o-nitrophenol,m-nitrophenol, p-nitorophenol, 2,4-dinitorophenol, 2,4,6-trinitorophenoland the like; monohydric phenols of polycyclic aromatic compounds suchas naphthol and the like. Each monohydric phenol can be used singly, ora s a mixture thereof.

(Polyhydric Phenol)

The polyhydric phenols mentioned above, include resorsin, alkylresorsin,pyrogallol, catechol, alkyl catechol, hydroquinone, alkyl hydroquinone,fluoroglrsin, bisphenol, dihydroxynaphthalene and the like. Eachpolyhydric phenol can be used singly, or as a mixture thereof. Resorsinand alkylresorsin are more suitable than other polyhydric phenols.Alkylresorsin is in particular the most suitable polyhydric phenolsbecause alkylresorsin can react with aldehydes more rapidly thanresorsin.

The alkylresorsins include 5-methyl resorsin, 5-ethyl resorsin, 5-propylresorsin, 5-n-butyl resorsin, 4,5-dimethyl resorsin, 2,5-dimethylresorsin, 4,5-diethyl resorsin, 2,5-diethyl resorsin, 4,5-dipropylresorsin, 2,5-dipropyl resorsin, 4-methyl-5-ethyl resorsin,2-methyl-5-ethyl resorsin, 2-methyl-5-propyl resorsin, 2,4,5-trimethylresorsin, 2,4,5-triethyl resorsin, and the like.

The polyhydric phenol mixture produced by the dry distillation of oilshale, which is produced in Estonia, is inexpensive and said polyhydricphenol mixture includes 5-metylresorcin, along with many other kinds ofalkylresorcin having a high reactivity, making said polyhydric phenolmixture is an especially desirable raw polyphenol material.

In the present invention, said phenolic compound and aldehyde and/oraldehyde donor (aldehydes) are condensed together. Said aldehyde donormeans a compound or a mixture which emits aldehyde when said compound orsaid mixture decomposes. The aldehydes include formaldehyde,acetoaldehyde, propionaldehyde, chloral, furfural, glyoxal,n-butylaldehyde, caproaldehyde, allylaldehyde, benzaldehyde,crotonaldehyde, acrolein, phenyl acetoaldehyde, o-tolualdehyde,salicylaldehyde and the like. The aldehyde donors includeparaformaldehyde, tiroxane, hexamethylenetetramine, tetraoxymethylene,and the like.

As described above, said phenolic resin is desirably sulfoalkylatedand/or sulfialkylated, to improve the stability of said water solublephenolic resin.

(Sulfomethylation Agent)

The sulfomethylation agents used to improve the stability of the aqueoussolution of phenol resins, include such as water soluble sulfitesprepared by the reaction between sulfurous acid, bisulfurous acid, ormetabisulfirous acid, and alkaline metals, trimethyl amine, quaternaryammonium (e.g. benzyltrimethylammonium); and aldehyde additions preparedby the reaction between said water soluble sulfites and aldehydes.

The aldehyde additions are prepared by the addition reaction betweenaldehydes and water soluble sulfites as mentioned above, wherein thealdehydes include formaldehyde, acetoaldehyde, propionaldehyde, chloral,furfural, glyoxal, n-butylaldehyde, caproaldehyde, allylaldehyde,benzaldehyde, crotonaldehyde, acrolein, phenyl acetoaldehyde,o-tolualdehyde, salicylaldehyde, and the like. For example,hydroxymethane sulfonate, which is one of the aldehyde additions, isprepared by the addition reaction between formaldehyde and sulfite.

(Sulfimethylation Agent)

The sulfimethylation agents used to improve the stability of the aqueoussolution of phenol resins, include alkaline metal sulfoxylates ofaliphatic or aromatic aldehyde such as sodium formaldehyde sulfoxylate(a.k.a. Rongalit), sodium benzaldehyde sulfoxylate, and the like;hydrosulfites (a.k.a. dithionites) of alkaline metal or alkaline earthmetal such as sodium hydrosulfite, magnesium hydrosulfite and the like;hydroxyalkanesulfinate such as hydroxymethanesulfinate and the like.

(Third Components)

In the case of producing said phenol resins, if necessary, additives maybe mixed in with said phenol resins as a catalyst or to adjust the pH,such additives including acidic compounds and alkaline compounds. Acidiccompounds include inorganic acid or organic acid such as hydrochloricacid, sulfuric acid, orthophosphoric acid, boric acid, oxalic acid,formic acid, acetic acid, butyric acid, benzenesulfonic acid,phenolsulfonic acid, p-toluenesulfonic acid, naphthalene-α-sulfonicacid, naphthalene-β-sulfonic acid, and the like; esters of organic acidsuch as dimethyl oxalate, and the like; acid anhydrides such as phthalicanhydride, maleic anhydride, and the like; salts of ammonium such asammonium chloride, ammonium sulfate, ammonium nitrate, ammonium oxalate,ammonium acetate, ammonium phosphate, ammonium thiocyanate, ammoniumimidosulfonate, and the like; halogenated organic compounds such asmonochloroacetic acid, the salt thereof, α,α′-dichlorohydrin, and thelike; hydrochloride of amines such as triethanolamine hydrochloride,aniline hydrochloride, and the like; urea adducts such as the ureaadduct of salicylic acid, urea adduct of stearic acid, urea adduct ofheptanoic acid, and the like; and N-trimethyl taurine, zinc chloride,ferric chloride, and the like.

Alkaline compounds include ammonia, amines; hydroxides of alkaline metaland alkaline earth metal such as sodium hydroxide, potassium hydroxide,barium hydroxide, calcium hydroxide, and the like; oxide of alkalineearth metal such as lime, and the like; salts of alkaline metal such assodium carbonate, sodium sulfite, sodium acetate, sodium phosphate, andthe like.

(Method of Producing the Phenol Resins)

The phenol resins (the precondensation polymers) can be prepared usingthe usual method. The usual methods include method (a) comprising thecondensation of a monohydric phenol and/or a polyhydric phenol andaldehydes; method (b) comprising the condensation of a precondensationpolymer and a monohydric phenol and/or a polyhyrdric phenol, whereinsaid precondensation polymer comprises a monohydric phenol andaldehydes; method (c) comprising the condensation of a precondensationpolymer and a monohydric phenol and/or a polyhydric phenol, wherein saidprecondensation polymer comprises a monohydric phenol, a polyhydricphenol and aldehydes; method (d) comprising the condensation of aprecondensation polymer consisting of a monohydric phenol and aldehydes,and said precondensation polymer consisting of a polyhydric phenol andaldehydes; method (e) comprising the condensation of a precondensationpolymer consisting of a monohydric phenol and aldehydes and/orprecondensation polymers consisting of a polyhydric phenol resin andaldehydes, and said precondensation polymer consisting of monohydricphenol and polyhydric phenol and aldehydes.

In the present invention, the desirable phenolic resin isphenol-alkylresorcin cocondensation polymer. Said phenol-alkylresorcincocondensation polymer provides a water solution of said cocondensationpolymer (pre-cocondensation polymer) having good stability, and beingadvantageous in that it can be stored for a longer time at roomtemperature, compared with a condensate consisting of a phenol only(precondensation polymer). Further, in a case where said porous material(2) into which said water solution is impregnated, is put to B-stage byprecuring, said porous material has good stability and does not lose itsmoldability after longtime storage. Further, since alkylresorcin ishighly reactive to aldehyde, and catches free aldehyde to react with it,the content of free aldehyde in the resin can be reduced.

Said phenol-alkylresorcin cocondensation polymer is also advantageous inthat the content of free aldehyde in said polymer is reduced by thereaction with alkylresorcin.

The desirable method for producing said phenol-alkylresorcincocondensation polymer is first to create a reaction between phenol andaldehyde to produce a phenolic precondensation polymer, and then to addalkylresorcin, and if desired aldehyde to said phenolic precondensationpolymer to create reaction. In the case of the method (a) for thecondensation of monohydric phenol and/or polyhydric phenol andaldehydes, the aldehydes (0.2 mole to 3 moles) are added to saidmonohydric phenol (1 mole), then said aldehydes (0.1 mole to 0.8 mole)are added to the polyhydric phenol (1 mole) as usual. If necessary,additives may be added to the phenol resins (the precondensationpolymers). In the method(s), there is a condensation reaction fromheating at 55° C. to 100° C. for 8 to 20 hours. The addition ofaldehydes may be made at once time at the beginning of the reaction, orseveral separate times throughout the reaction, or said aldehydes may bedropped continuously throughout the reaction.

In the case of sulfomethylation and/or sulfimethylation, thesulfomethylation agents and/or sulfimethylation agents may be added tothe precondensation at an arbitrary time.

The addition of the sulfomethylation agents and/or sulfimethylationagents may be made any time such as before, during, or after thecondensation. The total amount of said sulfomethylation agent and/orsulfimethylation agent added is usually in the range of between 0.001 to1.5 moles per 1 mole of phenol. In a case where said amount added isless than 0.001 mole, the hydrophile of the resulting sulfomethylatedand/or sulfimethylated phenolic resin is not adequate, and in a casewhere said amount added is more than 1.5 moles, water resistance of theresulting sulfomethylated and/or sulfimethylated phenolic resindegrades. To provide excellent curing properties in the resultingprecondensate and excellent physical properties in the cured resin, saidamount to be added is preferably in the range of between 0.01 to 0.8mole per 1 mole of phenol.

The sulfomethylation agents and/or sulfimethylation agents forsulfomethylation and/or sulfimethylation react with the methylol groupsand/or aromatic gropes, so that the sulfomethyl group and/or sulfimethylgroup are introduced to the precondensation prepolymers.

The solution of precondensation polymers of sulfomethylated and/orsulfimethylated phenol resins is stable widely even in acid condition(e.g. pH=1.0) or alkaline condition, so that the solution can be curedin any conditions such as acid, neutral or alkaline. In the case ofcuring the precondensate under acid condition, there is a decrease inthe remaining methylol groups, so that no formaldehydes from thedecomposed cured phenol resins appear.

Further, if necessary, the phenol resins and/or precpndensation polymersthereof may be copolycondensed with amino resin monomers such as urea,thiourea, melamine, thiomelamine, dicyandiamine, guanidine, guanamine,acetoguanamine, benzoguanamine, 2,6-diamino-1.3-diamine, and the like.

Further, curing agents such as an aldehyde and/or an aldehyde donor oran alkylol triazone derivative, and the like, may be added to saidphenolic precondensation polymer (including precocondensation polymer).

As said aldehyde and/or aldehyde donor, the same aldehyde and/oraldehyde donor as used in the production of said phenolicprecondensation polymer is (are) used, and an alkylol triazonederivative is produced by the reaction between urea group compound,amine group compound, and aldehyde and/or aldehyde donor. Said ureagroup compound used in the production of said alkylol triazonedderivative may be such as urea, thiourea, alkylurea such as methylurea,alkylthiourea such as methylthiourea; phenylurea, naphthylurea,halogenated phenylurea, nitrated alkylurea, and the like, or a mixtureof two or more kinds of said urea group compounds. In particular,desirable urea group compound may be urea or thiourea. As amine groupcompounds, aliphatic amine such as methyl amine, ethylamine,propylamine, isopropylamine, butylamine, amylamine and the like,benzylamine, farfuryl amine, ethanol amine, ethylmediamine,hexamethylene diamine hexamethylene tetramine, and the like, andfurther, ammonia are illustrated, and said amine group compound is usedsingly or two or more amine group compounds may be used together.

The aldehyde and or aldehyde donor used for the production of saidalkylol triazone derivative is (are) the same as the aldehyde and/oraldehyde donor used for the production of said phenolic precondensationpolymer.

To synthesize said alkylol triazone derivatives, commonly 0.1 to 1.2moles of said amine group compound(s) and/or ammonia, and 1.5 to 4.0moles of aldehyde and/or aldehyde donor are reacted with 1 mole of saidurea group compound.

In said reaction, the order in which said compounds are added isarbitrary, but preferably, first the required amount of aldehyde and/oraldehyde donor is (are) put in a reactor, then the required amount ofamine group compound(s) and/or ammonia is (are) gradually added to saidaldehyde and/or aldehyde donor, the temperature being kept at lower than60° C., then further, a required amount of said urea group compound(s)is (are) added to the resulting mixture at 80 to 90° C. for 2 to 3hours, being agitated to react together. Usually, 37% by mass offormalin is used as said aldehyde and/or aldehyde donor, but some ofsaid formalin may be replaced by paraform aldehyde to increase theconcentration of the reaction product.

Further, in a case where hexamethylene tetramine is used, the solidcontent of the reaction product obtained is much higher. The reactionbetween said urea group compound, said amine group compound and/orammonia and said aldehyde and/or aldehyde donor is commonly performed ina water solution, but water may be partially or wholly replaced by oneor more kinds of alcohol(s) such as methanol, ethanol, isopropanol,n-butanol, ethylene glycol, diethlene glycol, and the like, and one ormore kinds of other water soluble solvent(s) such as a ketone groupsolvent such as acetone, methylethyl ketone, and the like can also beused as solvent.

The amount of said curing agent to be added is, in the case of aldehydeand/or aldehyde donor, in the range of between 10 and 100 parts by massto 100 parts by mass of said phenolic precondensation polymer(precocondensation polymer), and in the case of alkylol triazone, 10 to50 parts by mass to 100 parts by mass of said phenolic precondensationpolymer (precocondensation polymer).

[Porous Material]

Said porous material (2) used in the present invention is made of anorganic fiber material or foamed plastics having an interconnected cellstructure. Said organic fiber of said porous material (2) is, forexample, a polyester fiber such as polyethylene telephthalate fiber,polybutylene telephthalate fiber, and the like, a synthetic fiber, suchas polyethylene fiber, polypropylene fiber, polyamide fiber, acrylicfiber, urethane fiber, polyvinylchloride fiber, polyvinylidene chloridefiver, acetate fiber, vinylon fiber, and the like, a semisyntheticfiber, such as rayon fiber, and the like, a natural fiber, such ascoconut fiber, hemp fiber, kenaf fiber, bamboo fiber and the like or areclaimed fiber obtained by fiberizing a fiber product made of saidfiber(s). Said fiber is singly usable or two or more kinds of saidfibers may be used.

Said foamed plastics include, for example, foamed polyester, such asfoamed polyethylene telephthalate, foamed polybutylene telephthalate,and the like, foamed polyethylene, foamed polypropylene, foamedpolyamide, foamed acrylic resin, foamed urethane resin, foamedpolyvinylchloride, foamed polyvinylidenechlorde, foamed acetate, and thelike.

The common unit weight (g/m²) of said porous material used in thepresent invention is 200 g/m² to 100 g/m².

Further, the fiber used in said porous material of the present inventionmay be treated with a flame-retardant.

The fineness of said fiber of said porous material (2) is preferably0.02 dtex to 50 dtex, but more preferably 0.1 dtex to 30 dtex.

In a case where the fineness is less than 0.02 dtex, the rigidity of theresulting sound absorber (1) may degrade, and in a case where thefineness is greater than 50 dtex, the resulting sound absorber hasinsufficient sound absorbability.

Said phenolic precondensation polymer is impregnated into said porousmaterial (2) using well known methods such as the dipping method, spraymethod, flow coating method, roll coating method, and the like.

For instance, as shown in FIG. 3, said porous material (2) is pulled outfrom a roll (2A) of said porous material (2) to be introduced into atank (7) filled with phenolic precondensation polymer (water solution S)through guide rolls (4, 5, 6) which impregnate said phenolicpresondensation polymer into said porous material(2). If desired, saidporous material (2) into which said precondensation polymer isimpregnated may be squeezed with a squeezing roll (8) to adjust amountof said precondensation polymer to be impregnated therein.

Said phenolic resin is fire resistant, and by adjusting the content ofsaid phenolic resin in said porous material (2), the fire resistance ofsaid sound absorber (1) can be adjusted. The desirable amount of saidphenolic resin to be contained in said porous material (2) may be 50 to200% by mass, more desirably 55 to 170% by mass, but ideally 60 to 150%by mass, per 1 m² of said porous material (2)(g/m²), and in a case wherethe content of said phenolic resin is less than 50% by mass per 1 m² ofsaid porous material (2)(g/m²), the fire resistance of the resultingsound absorber (1) degrades, and in a case where the content of saidphenolic resin is greater than 200% by mass, the sound absorbability ofsaid sound absorber becomes inferior.

[Manufacture of Said Fire Resistant Sound Absorber]

A prescribed amount of said phenolic precondensation polymer isimpregnated into said porous material (2), after which and then saidporous material (2) is dried and pre-cured. Said drying process iscarried out by blowing hot air onto said porous material (2), and duringsaid drying process, decompression may occur.

During said pre-curing process, said precondensation polymer may becured completely, but preferably cured to be at its B-stage. Said porousmaterial (2) containing said precondenstion polymer at its B-stage hasgood moldability, and can be stored for a long time.

After said pre-curing process, said porous material (2) is then moldedby hot press molding to produce said sound absorber (1). In said hotpress molding, for instance, a molding machine having a lower mold paneland an upper mold panel, having desired shaped mold faces is used, and ahood silencer (1) having a prescribed shape, as shown in FIG. 1, isproduced.

Said fire resistant sound absorber (1) of the present invention can beused as a sound absorber (1) without being laminated with a fireresistant surface material, and the like.

Further, said fire resistant sound absorber (1) of the present inventionmay be single or multi-layered.

Still further, a fiber sheet made of above mentioned synthetic fiber orthe like may be laminated onto one or both side(s) of said fireresistant sound absorber (1) as either surface material or back sidematerial.

If desired, in the present invention, amino group monomers such as urea,thiourea, melamine, thiomelamine, dicyandiamide, guanidine,acetogunamine, benzoguanamine, 2,6-diamino-1,3-diamine and the like, aprecondensation polymer of said amino group monomer, emulsion or watersolution or a powder of a thermoplastic resin such as polyethylene,polypropylene, ethylene-propylene copolymer, ethylene-vinylacetatecopolymer, polyvinylacetate, polyarylic ester, polystyrene,styrene-butadiene copolymer, acrylonitorile-butadiene copolymer,acrylonitrile-butadien-styrene terpolymer, a polyamide having a lowmelting point, polyester having a low melting point, and the like; anatural rubber and derivatives thereof; fillers and surfactants such ascalcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate,calcium sulfurous acid, calcium phosphoric acid, calcium hydroxide,magnesium hydroxide, aluminum hydroxide, magnesium oxide, titaniumoxide, iron oxide, zinc oxide, aluminum oxide, silica, diatomaceousearth, dolomite, gypsum, talc, clay, asbestos, mica, calcium silicate,bentonite, white carbon, carbon black, iron powder, aluminum powder,glass powder, stone powder, synthetic resin powder, furnace slag,flyash, cement, zirconia powder, linter, linen, sisal, wood flour, wheatflour, walnut flour, starch, coconut shell flour, rice powder, activatedcarbon, charcoal, bark, chitosan; higher fatty acids such as stearicacid, palmitin acid and the like; higher alcohols such as palmitinalcohol, stearyl alcohol and the like; an ester of fatty acid such asbutylstearate, glycerin monostearate and the like; amides of fatty acid;a natural wax such as carnauba wax and the like; synthetic wax;plasticizers, such as pigment, dye, fire retardant, smoke retardant,insect repellent, antiseptic, antioxidant, ultraviolet absorber,fluorescence dye, surfactant, foaming agents, oil repellent, dioctylphthalate (DOP), dibutyl phthalate (DBT) and the like; antioxidants,anti-static additives, crystallization promoters, and the like; theabove-mentioned third components may be concontained.

Said third component(s) may be added directly to or coated on saidporous material(s) or said third component(s) may be added to saidprecondensation polymer of said phenolic resin which is impregnated intosaid porous material(s).

Said fire resistant sound absorber (1) of the present invention is usedas cylinder head-cover silencer, engine undercover silencer, outer dashsilencer, dash silencer, room partition silencer, ceiling material,interior material and the like which are used in a car, and as abuilding material, and the like. Said fire resistant sound absorber isespecially useful as a hood silencer which is requested to be fireresistant (heat resistant), and have sound absorbability. The presentinvention is described in detail by the following EXAMPLES, but thescope of the present invention should not be limited by these EXAMPLES.

EXAMPLE 1

A 60% by mass (solid) of a phenol holmaldehyde precondensation polymer(phenolic resin precondensation polymer) was impregnated into a sheetmade of needle punched polyethylene telephthalate fiber (unit weight 400g/m² thickness 10 mm). The amount of said precondensation polymerimpregnated therein was adjusted to be 50% by mass (solid of phenolicresin) per unit weight of said sheet.

Said sheet, impregnated with said phenolic resin precondensationpolymer, was dried at 150° C. to precure and after precuring, washot-pressed at 200° C. for 60 seconds, and a molded into a sheet with athickness of 5 mm (EXAMPLE 1).

EXAMPLES 2 and 3

Said phenolic resin precondensation polymer of EXAMPLE 1 was impregnatedinto said sheet of EXAMPLE 1, the amount of said phenolic resin to beimpregnated therein was adjusted to be 100% and 200% by mass (solid) perunit weight of said sheet. Said sheets were precured and hot-pressed thesame as in EXAMPLE 1, producing molded sheets with a thicknesses of 5mmeach (EXAMPLES 2 and 3).

COMPARISONS 1 and 2

Said phenolic resin precondensation polymer of EXAMPLE 1 was impregnatedinto said sheet of EXAMPLE 1, and the amount of said phenolic resinimpregnated therein was adjusted to be 40% and 250% by mass (solid) perunit weight of said sheet. Said sheets were precured and hot-pressed thesame as in EXAMPLE 1, producing molded sheets with a thickness of 5 mmeach (COMPARISOMS 1 and 2).

(Burning Test)

A burning test according to the FMVSS-302 horizontal test, was performedon each molded sheet from EXAMPLES 1 to 3, and COMPARISONS 1 and 2. Theresults are shown in Table 1.

(Sound Absorption Test)

A sound absorbing test according to the JIS-A1405 was performed on eachmolded sheet from EXAMPLES 1 to 3 and COMPARISONS 1 and 2. The resultsare shown in Table 1. TABLE 1 Molded sheet Sound Absorbability (%)(Sound 500 1000 2000 4000 absorber) Burnig test Hz Hz Hz Hz EXAMPLE 1Fire retardancy 35 45 80 83 EXAMPLE 2 Nonflammability 35 50 85 84EXAMPLE 3 Nonflammability 30 45 80 75 COMPARISON 1 Slow flammability 3040 65 60 COMPARISON 2 Nonflammability 15 20 45 40

Referring to the results in Table 1, the molded sheets into whichphenolic resin has been impregnated in amounts of 50% by mass, 100% bymass, 200% by mass, and 250% by mass per unit weights of said sheets(EXAMPLES 1 to 3 and COMPARISONS 2) each exhibit fire retardation ornonflammability, while a molded sheet into which phenolic resin has beenimpregnated in an amount of 40% by mass shows slow flammability.

Further, as for the results of the sound absorption test, it wasconfirmed that the molded sheets of EXAMPLES 1 to 3 and COMPARISON 1each have sufficient sound absorbability while the molded sheet intowhich phenolic resin has been impregnated in an amount of 250% by mass(COMPARISON 2) has insufficient sound absorbing qualities.

EXAMPLE 4

A 55% by mass solution (solid) of a phenol-alkylresorcin-formaldehydeprecocondensation polymer (phenolic resin precocondensation polymer) wasimpregnated into a sheet made of needle punched polypropylene fibers(fineness 0.02 dtex, unit weight 300 g/m², thickness 15 mm). The amountused to impregnate was adjusted to be 70% by mass (solid of phenolicresin) per unit weight of said sheet.

Said sheet into which said phenolic resin precocondensation polymer wasimpregnated was then dried at 150° C., and procured, and afterprecuring, said sheet was hot-pressed at 200° C. for 45 seconds,producing a molded sheet with a thickness of 7 mm (EXAMPLE 4).

EXAMPLES 5 and 6

Said phenolic resin precocondensation polymer from EXAMPLE 4 wasimpregnated into two separate sheets made of needle punchedpolypropylene fiber (fineness 20 dtex, unit weight 300 g/m², thickness15 mm) and (fineness 50 dtex, unit weight 300 g/m², thickness 15), andthe amounts of said phenolic resin to be impregnated therein were eachadjusted to be 70% by mass per unit weights of said sheets, followingwhich each sheet was precured and hot-pressed the same as in EXAMPLE 4,producing molded sheets with thickness of 7mm (EXAMPLES 5 and 6).

COMPARISONS 3 and 4

Said phenolic resin precocondensation polymer of EXAMPLE 4 wasrespectively impregnated into two seperate sheets made of needle punchedpolypropylene fiber (fineness 0.1 dtex, unit weight 300 g/m², thickness15 mm) and (fineness: 60 dtex, unit weight 300 g/m², thickness 15 mm),the amounts of said phenolic resin to be impregnated therein were eachadjusted to be 70% by mass per unit weight of said sheets, and eachsheet was precured and hot-pressed the same as in EXAMPLE 4, producingmolded sheets with a thickness of 7 mm each (COMPARISONS 3 and 4).

A rigidity test, burning test, and sound absorption test were performedon said molded sheets of EXAMPLES 4, 5, and 6, and COMPARISONS 3 and 4.The results are shown in Table 2. Said rigidity test is performedaccording to JIS-K6911, General test method for measuring thermoplasticresin 5.17 bending strength. Concerning the burning test and soundabsorption test, the same methods as in EXAMPLES 1 to 3, and COMPARISONS1 and 2 were applied. TABLE 2 Molded sheet Rigidity test Soundabsorbability (%) (sound absorber) (N/mm²) Burning test 500 Hz 1000 Hz2000 Hz 4000 Hz EXAMPLE 4 1.5 Nonflammability 40 68 95 90 EXAMPLE 5 1.8Nonflammability 33 60 90 83 EXAMPLE 6 1.7 Nonflammability 30 55 85 83COMPARISON 3 0.8 Nonflammability 42 70 95 92 COMPARISON 4 1.5Nonflammability 18 22 48 45

In said rigidity test, it was recognized that the molded sheets made offiber with a finesses of 0.02 dtex, 20 dtex, 50 dtex and 60 dtex arerigid enough to be the sound absorbers, (EXAMPLES 4, 5, and 6, andCOMPARISON 4), while molded sheet with a fineness of 0.Oldtex lacked thesufficient rigidity as the sound absorber (COMPARISON 3). The testresults suggest that every molded sheet (EXAMPLES 4, 5, and 6, andCOMPARISONS 3 and 4) was nonflammable.

Referring to the results of the sound absorption test, said fiber moldedsheet with a fineness of 60 dtex, has insufficient sound absorbability(COMPARISON 4).

The above test results suggest that said molded fiber sheet with afineness of less than 0.02 dtex has lacked sufficient rigidity, and thatsaid fiber molded sheet with a fineness greater than 50 dtex isinsufficiently sound absorbent.

EXAMPLE 7

A 60% by mass solution (solid) of a phenol-alkylresorcin-holmaldehydeprecocondensation polymer and alkylol triazone derivative wasimpregnated into a sheet made two kinds of needle punched polyesterfibers (40% by mass, with a fineness of 0.3 dtex) and (60% by mass witha fineness of 8 dtex). The amount of said precondensation polymer to beimpregnated therein was adjusted to be 100% by mass (solid) per unitweight of said sheet, and an alkylol triazone derivative was added in anamount of 50 parts by mass to 100 parts by mass of 60% by masssolution(solid) of said precocondensation polymer.

Said sheet, into which said precocondensation polymer was impregnated,was precured at 120° C., after which, said sheet was hot-pressed at 210°C. for 70 seconds, producing a molded sheet with a thickness of 10 mm(EXAMPLE 7 ).

EXAMPLES 8 and 9

Said phenolic resin precocondensation polymer of EXAMPLE 7 wasimpregnated into two separate polyester fiber sheets from EXAMPLE 7,each with a unit weights of 100 g/m² and 800 g/m², with the amount ofsaid phenolic resin precocondensation polymer for impregnation beingadjusted to be 100% by mass (solid) per unit weight of each sheet, eachsheet being precured and hot-pressed the same as in EXAMPLE 7, to bemolded sheets, each with a thicknesses of 10 mm (EXAMPLES 8 and 9).

COMPARISONS 5 to 10

Said phenolic resin precocondensation polymer used in EXAMPLE 7 wasimpregnated into the three kinds of sheets (unit weights 40 g/m², 100g/m², and 800 g/m²) used in EXAMPLES 7, 8 and 9, the amounts to beimpregnated being adjusted to be 30% by mass and 250% by mass as solidof said phenolic resin per unit weight of said sheets, following whichsaid sheets were precured and hot-pressed in the same way as in EXAMPLE7, to be molded sheets each with a thickness of 10 mm.

-   COMPARISON 5 (unit weight of sheet 40 g/m², amount of resin    impregnated therein 30% by mass).-   COMPARISON 6 (unit weight of sheet 100 g/m², amount of resin    impregnated therein 30% by mass).-   COMPARISON 7 (unit weight of sheet 800 g/m², amount of resin    impregnated therein 30% by mass).-   COMPARISON 8 (unit weight of sheet 40 g/m², amount of resin    impregnated therein 250% by mass).-   COMPARISON 9 (unit weight of sheet 100 g/m², amount of resin    impregnated therein 250% by mass).-   COMPARISON 10 (unit weight of sheet 800 g/m², amount of resin    impregnated therein 250% by mass).

Rigidity test, burning test, and sound absorption test were performed oneach of said molded sheets from EXAMPLES 7 to 9 and COMPARISONS 5 to 10.The same test methods were applied. The results are shown in Table 3.TABLE 3 Molded sheet Rigidity test Sound absorbability (%) (soundabsorber) (N/mm²) Burning test 500 Hz 1000 Hz 2000 Hz 4000 Hz EXAMPLE 71.4 Nonflammability 30 45 80 82 EXAMPLE 8 2.2 Nonflammability 30 50 9290 EXAMPLE 9 3.8 Nonflammability 28 60 90 84 COMPARISON 5 0.5 Slowflammability 25 40 78 80 COMPARISON 6 0.8 Slow flammability 25 46 75 74COMPARISON 7 0.9 Slow flammability 28 45 85 78 COMPARISON 8 1.8Nonflammability 15 30 50 45 COMPARISON 9 2.9 Nonflammability 20 33 55 52COMPARISON 10 4.1 Nonflammability 18 26 54 55

The results of the rigidity test make clear that said molded sheets ofEXAMPLES 7 to 9, each have sufficient rigidity for a sound absorbingmaterial, and that said molded sheets of COMPARISONS 8 to 10 each alsohave sufficient rigidity while said molded sheets of COMPARISONS 5 to 7each have insufficient rigidity for a sound absorbing material.

The results of the burning test make clear that said molded sheets ofEXAMPLES 7 to 9 are each fire resistant, and that said molded sheets ofCOMPARISONS 8 to 10 are each also fire resistant, while said moldedsheets of COMPARISONS 5 to 7 into which the amount of said phenolicresin impregnated was respectively 30% by mass per unit weight for eachof said sheets, have respectively slow flammability, not fire resistanceor nonflammability.

The results of the sound absorption test show that said molded sheets ofEXAMPLES 7 to 9 have better sound absorbability than said molded sheetsof COMPARISONS 5 to 10 at any frequency. Further, it was recognized thatsaid molded sheets of COMPARISONS 8 to 10 which contain said phnolicresin in an amount of 250% per mass for unit weight have particularlypoor sound absorbability.

The above described test results suggest that in a case where saidmolded sheet contains said phenolic resin in an amount of less than 50%by mass per unit weight of said sheet, said molded sheet becomes notfire resistant, and in the case where said molded sheet contains saidphenolic resin in an amount of more than 200% by mass per unit weight ofsaid molded sheet said molded sheet has poor sound absorbability.

EXAMPLE 10

As shown in FIG. 3, 60% by mass (solid) of a phenol formaldehydeprecondensation polymer (phenolic resin precondensation polymer) wasimpregnated in a sheet made of needle punched polyester (polyethylenetelephthalate fiber) with a fineness of 10 dtex), and with a unit weightof 400 g/m² and thickness of 10 mm. The amount of said precondensationpolymer to be impregnated therein was adjusted to be 50% by mass assolid per unit weight of said sheet.

Said sheet into which said phenolic resin precondensation polymer wasimpregnated was dried and precured at 150° C., to put said phenolicresin at its B-stage, after which said sheet was hot-pressed at 200° C.for 60 seconds using a molding machine, having upper and lower moldparts, both having desirably shaped mold faces, to obtain a hoodsilencer (1), having a prescribed shape as shown in FIG. 1. As shown inFIG. 2, said hood silencer (1) was attached to the underside of the hoodpanel (3). Said hood silencer (1) was easily handled, so has goodworkability, and was easily attached to said hood panel (3).

Further, less dust flew about from said hood silencer (1), maintaining agood working environment.

Further, said hood silencer (1) had excellent rigidity, soundabsorbability and fire resistance.

EXAMPLE 11

A 55% by mass (solid) of a phenol-alkylresorcin precocondensationpolymer into which 5% by mass of a fluorocarbon water repellent agent,and 3% by mass of a phosphoric fire retardant were mixed, wasimpregnated into a sheet made of a fiber mixture consisting of 30% bymass of polyester fiber with a fineness of 1.5 dtex, 40% by mass ofpolyester fiber with a fineness of 10 dtex, 20% by mass of hemp fiberwith a fineness of 45 dtex, and 5% by mass of low melting pointpolyester fiber with a fineness of 6 dtex and melting point of 110° C.,said sheet being manufactured by heating said fiber mixture at 130° C.,melting said low melting point polyester fiber in a heating chamber, andthen pressing said fiber mixture with a cooling roll, to adjust itsthickness to 15 mm, and unit weight per said sheet to 500 g/m².

The amount of said phenolic resin to be impregnated therein was adjustedto be 70% by mass (solid) per unit weight of said sheet.

Said sheet into which said precocondensation polymer was impregnated,was then dried and precured at 100° C., after which, said sheet washot-pressed at 200° C. for 65 seconds to obtain a sound absorber(EXAMPLE 11). Said sound absorber was fire resistant, having excellentrigidity and sound absorbability.

EXAMPLE 12

A 50% by mass (solid) of a sulfomethylated phenol-alkylresorcinprecocondensation polymer was impregnated into a sheet made of a needlepunched fiber mixture of polypropylene fiber with a fineness of 0.5dtex(40% by mass), rayon fiber with a fineness of 6 dtex (30% by mass),polyamide fiber with a fineness of 3 dtex (5% by mass), kenaf fiberswith a fineness of 45 dtex (25% by mass), the unit weight of said sheetbeing 100 g/m², and thickness 10 mm.

The amount of said phenolic resin to be impregnated therein was adjustedto be 80% by mass (solid) per unit weight of said sheet.

Said sheet into which said precocondensation polymer was impregnated,was dried and precured at 120° C., after which 3 pieces of said sheetwere laminated to each other, and then said laminated sheets werehot-pressed at 200° C. for 70seconds to obtain a sound absorber (EXAMPLE12).

Said sound absorber was fire resistant, with excellent rigidity andsound absorbability.

EXAMPLE 13

A 50% by mass (solid) of a sulfomethylated phenol-alkylresorcinprecocondensation polymer and alkylol triazone derivative wasimpregnated into a sheet made of a needle punched fiber mixture ofpolypropylene fiber with a fineness of 0.5 dtex (40% by mass), rayonfiber with a fineness of 6 dtex (30% by mass), polyamide fiber with afineness of 3 dtex (5% by mass), and bamboo fiber with a fineness of 45dtex (25% by mass), the amount of said phenolic resin to be impregnatedtherein was adjusted to be 80% by mass (solid) per unit weight of saidsheet.

Sixty parts by mass of said alkylol triazone derivative were mixed into100 parts by mass of said precocondensation polymer whose solid contentwas 50% by mass.

Said sheet into which said precocondensation polymer was impregnated,was then dried and precured at 120° C., after which three pieces of saidprecured sheets were laminated to each other, and said laminated sheetswere hot pressed at 200° C. for 70 seconds to obtain a sound absorber(EXAMPLE 13). Said sound absorber was fire resistant, and had excellentrigidity and sound absorb ability.

1. A fire resistant sound absorber made of a porous material into whicha phenolic resin is impregnated, wherein said phenolic resin isimpregnated in an amount in the range of between 50 and 200% by mass per1 m² of said porous material and said porous material consists of fibershaving a fineness in the range of between 0.02 dtex and 50 dtex.
 2. Afire resistant sound absorber in accordance with claim 1, wherein saidphenolic resin is a cocondensation polymer of phenol-alkylresorcin.
 3. Afire resistant sound absorber in accordance with claim 2, wherein saidphenol-alkylresorcin cocondensation polymer is produced by addingalkylresorcin to phenolic resin precondensation polymer to cocondensate.